The present invention relates to a microfluidic flow device for determining parameters of a physical and/or chemical transformation, and also to the use of such a microfluidic flow device.
The term “transformation” is used to cover any type of interaction that may take place in a mixture of at least two components. In non-limiting manner, the transformation may be a reaction of chemical and/or physical type, such as for example, any conventional type of chemical reaction, and also crystallization or precipitation, or indeed a change in a liquid/vapor equilibrium, amongst others. In general, in the meaning of the invention, such a transformation can involve chemical phenomena, with electrons being exchanged or being shared, physical interactions or repulsions, such as hydrogen bonds, electrostatic interactions, steric attractions or repulsions, affinities for different hydrophilic and/or hydrophobic media, formulation stabilities, flocculation, or indeed phase transfers, e.g. of liquid/liquid, solid/liquid, or gas/liquid type.
In the meaning of the invention, the parameters of such a transformation are, in non-limiting manner, the rate of chemical reaction in a uniform or non-uniform medium, the conditions that enable an optimum yield to be obtained for chemical reactions, reaction enthalpies, processes over time involving chemical and physical reactions, and also solubility diagrams or phase diagrams.
In conventional manner, a microfluidic flow device comprises at least one microchannel enabling at least one fluid to flow. The characteristic dimension of each microchannel, in the context of the invention, lies in the range a few micrometers to one millimeter. Typically, such a dimension causes flow to be substantially laminar within the microchannel, having a Reynolds number of less than 1.
A microfluidic flow device is known from the article “Quantitative analysis of molecular interaction in a microfluidic channel: The T-sensor” (Anal. Chem. 1999, 71, 5340-5347) referred to below as Yager et al. That flow device comprises two upstream channels together with a single downstream channel defining a T-shape. That publication describes the possibility of causing a target fluid to flow together with a fluorescent indicator within the downstream channel so as to determine the concentration of the target fluid by measuring fluorescence in a region of said channel, in which mutual diffusion takes place between the target fluid and the indicator.
The application of a microfluidic flow device for determining parameters of a chemical type transformation is known from the article “A microfluidic system for controlling reaction networks in time” (Angewandte Chemie, International Edition 2003, 42, 767-772), which is referred to below as Ismagilov et al. The arrangement of that device involves two inlets for respective fluids that are suitable for reacting together. Those two reagents are initially put into contact with a separator fluid in order to avoid early reaction, then they are mixed with a non-miscible fluid, typically oil. That leads to dispersed entities being formed, i.e. a succession of drops, each of which comprises a mixture of the two above-mentioned reagents.
Under those conditions, when a chemical reaction occurs, each drop constitutes a microreactor, with the composition thereof varying along the microchannel. The microchannel is also provided with zigzags that contribute to deforming flow within the drops, thus making it possible to improve mixing between two reagents. The way the composition varies within each drop is measured optically, in particular by fluorescence.
Finally, the publication “Microfluidic routes to the controlled production of nanoparticles” (Chem. Commun., 2002, 1136-1137), referred to below as de Mello et al., describes the formation of nanoparticles of CdS. The corresponding reaction is tracked by absorption. That article emphasizes the fact that the microfluidic solution makes it possible in particular to improve uniformity along the reaction volume.
One of the advantages of the microfluidic solution is that it makes it possible to use only a very small quantity of fluid. Furthermore, it makes it easy to vary the composition of the mixture of the components under study, by modifying the flow rates thereof. However, the solution disclosed by Ismagilov et al. is found to be relatively unsatisfactory, in particular in that it does not make it possible to determine effectively the parameters of the transformation it sets out to study.
Furthermore, and in general, there exists a continuing need in industry to develop new products, presenting new properties, e.g. new chemical compounds or new compositions comprising new chemicals and/or new associations of chemicals. The physical and/or chemical transformations of substances are properties that are important for a good many applications, and it is often necessary to test them in research and development processing. There exists a need in terms of methods and installations for accelerating research and development processing, e.g. for testing a large number of substances and/or for performing tests on the smallest possible quantities of substances, and/or for performing tests more quickly, and/or for performing tests relating to transformations that are too slow to be studied in the device proposed by Ismagilov.